


The Trouble with Twins

by Canadian_BuckBeaver, Saiyurimai



Category: Undertail - Fandom, Undertale (Video Game)
Genre: Alternate Timelines, Alternate Universe - Coffee Shops & Cafés, Alternate Universe - Soulmates, Alternate Universe - Twins, Bad Pick-Up Lines, Bad Puns, Established Relationship, F/M, Flirting, Good W. D. Gaster, Grillster, Implied Sexual Content, Implied/Referenced Incest, M/M, Multi, Original Character(s), Papyrus (Undertale) Remembers Resets, Polyamory, Scientist W. D. Gaster, Sibling Incest, Underswap Papyrus (Undertale), Underswap Sans (Undertale), Undertale Monsters on the Surface, Undertale Saves and Resets, Walk Into A Bar
Language: English
Status: In-Progress
Published: 2019-02-13
Updated: 2019-02-12
Packaged: 2019-10-27 06:43:53
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 2
Words: 2,819
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/17761787
Author URL: https://archiveofourown.org/users/Canadian_BuckBeaver/pseuds/Canadian_BuckBeaver, https://archiveofourown.org/users/Saiyurimai/pseuds/Saiyurimai
Summary: The Undertale Monsters again have found themselves on to Surface.  Again, peace has befallen the monsters.For some, not all.For Stretch, Gaster and Grillby, peace will come once their soulmates are found and in their arms again. But this timeline, though first appearing like all the others, have some surprises in store for our favourite monsters.  Bucky and Sai aren't the same as they once were.  Can you say, double trouble?





	1. Stretch

**Author's Note:**

  * For [Saiyurimai](https://archiveofourown.org/users/Saiyurimai/gifts), [Canadian_BuckBeaver](https://archiveofourown.org/users/Canadian_BuckBeaver/gifts).



> Another amazing story co-authored by the Superb Saiyurimai and I
> 
> This is OC-centric, it has been tagged, you have all been warned ;)

Stretch was starting to get frustrated. He’d been on the surface now for months, having escaped along with the other monsters trapped in the Underground once the barrier had been lifted. Where in the hell could she be? He’d been searching non stop, top to bottom, always keeping an eye out for her and yet…He sighed and leaned back on the couch, staring up at the ceiling of the home he shared with his brother Blue who was currently out working and would probably be texting him soon to make sure he wasn’t napping the day away.

Ever since the Reset he’d been anxious to find her, Bucky. His Bucky. His adorable soul mate. He hated the resets, it made finding her and spending their lives together all that more difficult. He always had to start over with her. Although he admitted it was getting pretty easy to woo her after all of these times. Now if only he could find her and get it started. He knew Gaster and Grillby were having issues as well finding their Sai too. Maybe they just came while the girls were all on vacation or something? He glanced at the time and sighed. He might as well try the coffee shop again, maybe this time she’ll be there.

He made sure to check his pockets before teleporting to the front of the coffee shop, making sure to try and appear natural as if he hadn’t just popped into existence. Walking in he stepped in line, glancing around the café to see if Bucky was among the other customers. Of course she wasn’t. He was starting to get disheartened. He should have met her by now. He gave his order and made himself comfortable at a table and started to scroll through his phone while he drank his honey flavored tea. He wasn’t sure how long he had been sitting there playing a game on his phone when a jolt went through his bones at the sound of a far too familiar giggle.

If his skull could fall off it would of with the force of him whipping it around towards the voice his soul new far too well. “Yeah no I don’t think so. Pretty sure he would’ve asked us to stay longer if that was the case.” Bucky smiled at her companion that he couldn’t quite see from behind a few other customers but he didn’t care. She was here! He allowed himself a moment of absolute excitement, before he tried to figure out a way to approach her. He’d thought about it for ages but now that she was right here, right there in front of him, his mind was going blank.

Maybe he would wait until she’d gotten her coffee, then he could go up with a funny coffee pun and- Stretch paused. Seeing Bucky’s companion for the first time as the crowd shifted his sockets widened. No. Way. He was not seeing what he thought he was seeing. Of course he knew it was a possibility, all the timelines were different and he was never quite sure which one he was in until something like this…He shook his head, mouth agape as he watched Bucky and her identical twin go up to the counter and order the exact same thing. The two of them talking to one another with an all too familiar face. He couldn’t believe it. He’d been waiting all this time for her, looking for her only to have two of them show up.

The girls took a seat at a table not too far away from him, both wearing scrubs and their badges from a local hospital not too far away from the café. Of course. He hadn’t thought about the damn hospital! But he wasn’t exactly the type to just need to go to the hospital. He was a monster and just needed magic most of the time as opposed to human medicine. It was so weird, seeing two of her, laughing and talking with one another. Twice as many smiles, those sweet giggles, another warm body in his bed to curl up with at night and keep safe. Stretch was getting ahead of himself. He wasn’t even sure if they would be willing to share or if he would have to choose between the two. But how could he ever? He didn’t even know which one was Bucky.

He took a steadying breath and collected his thoughts. It was now or never. He had to try something, anything. He cleared his throat to get their attention, suddenly feeling nervous as two pairs of sky blue eyes looked up at him curiously. “U-uh, hello there. How do you brew?” for a moment he was afraid his words had overstepped his bounds but was rewarded with two sets of that glorious giggle he loved so much. “Name’s Stretch, mind if I have a seat?” He asked, the girls looking at one another thoughtfully before shrugging and motioning for him to sit next to them.

“Nice to meet you, I’m Britney and this is my sister Bucky.” Britney, extended her hand and then Bucky, Stretch’s soul thumping hard enough in his chest that he was sure they could hear it slamming against his rib cage. Stars they were amazing. Slipping into conversation with the two of them was as easy as it always was. He slipped in his flirty puns, “Careful of that coffee, it’s super hot. Oh wait, sorry you don’t need to worry too much, its not nearly as hot as you two ladies.” Or “No need to add any more sugar, you’re already too sweet.” Many of them were met with giggles or eye rolls and puns of their own. Bucky looked at her watch at one point and gasped.

“Shoot. We’ve gotta get going. Our next shift starts soon. But, uhm. I like the way you espresso yourself Stretch. What do you think we do this again some time?” Bucky smiled, a faint blush to her cheeks as she and Britney stood up, gathering their things.

“Yeah, I think we can agree that there’s something brewing between us here right? Maybe you just give us a call next time you want to grab some coffee?” Britney smiled, reaching into her bag and writing out two numbers on a piece of scrap paper, handing it over to him. Stretch nodded, taking the paper, seeing both of their names next to their numbers.

“I’d love to. It was nice meeting you ladies. Java good day.” He winked leaving the twins laughing and waving him off as he watched them go, his soul going with them. He let out a sigh and grabbed his coffee and short cut his way back to his place, feeling like he was walking on air. By the time Blue got home the smile still hadn’t left his face, seemingly permanently etched into his skull.

“WHAT’S GOT YOU IN A GOOD MOOD BROTHER?” Blue asked curiously, going into the kitchen and setting the groceries down on the counter as Stretch hummed softly.

“Oh nothing. Just met the loves of my life today. And I got their numbers.” He had already programmed their numbers into his phone and had sent them off a text message setting up a coffee date for the next day. “You know. The usual.” He was on cloud nine. Nothing could bring him down.

Blue looked over his brother and gave a soft smile with a shake of his head. It was about time his brother had found Bucky. He’d be in a much better mood from now on. Which meant a much better time being at home. “GREAT. NOW IF ONLY YOU CAN ALSO PICK UP YOUR SOCKS AND DO THE DISHES EVERY NOW AND THEN WE’D BE ALL SET HERE.” Blue teased, happy to hear the chuckle from his brother who started working on the dishes. Surprising Blue. Wow, he must be in a really, really great mood. That’s when he did a double take, “WAIT A SECOND. DID YOU SAY LOVES AS IN…MORE THAN ONE?"


	2. Grillby and Gaster

It had been a long and tedious day at work.  But home seemed like it wouldn’t be much better.  It just wasn’t home when she wasn’t here.  Like a body without a soul, there was no purpose to these empty walls and windows.  Sure, here on the Surface you could see the sun and stars, but what was the sun when it held no light or heat?  Just another light in the sky.

Grillby unlocked the door of the house that he shared with his partner.  At least in this timeline humans seemed to be more accepting of the monsters.  There was less tension, less violence between the two races.  Perhaps the resets had served a purpose after all.  Entering the flat, the flame monster looked around.  Gaster was silently scrolling through his phone, his laptop settled across from him. It looked like he had some facial recognition software flipping through social media pictures.  The skeleton monster had been in the same position since Grillby had first left in the morning.  It looked (and smelled) like the monster hadn’t moved a muscle since the morning.  Glancing up at him quickly, Grillby decided against asking him how the search was going or how his day was.  He already knew.  He knew that posture all too well.  Straight back, tense shoulders, and a straight smile.  Things weren’t going well as Gaster was slowly growing angry.

Silently, Grillby began to put the few groceries away.  He had just finished his day shift at the local restaurant, spent the entire day chopping and preparing vegetables, starting simmering soups and chilis for the evening staff.  During his breaks he had wandered the local mall and poked into the coffee chain beside them.  There was not even a hair of her.

Gaster had not been still.  He had been busy readjusting to life on the Surface again, restarting his various experiments for his studies and grants.  And yet, his mind never shut off.  Every crowd would be scanned.  He would go out of his way to go through stores and shops and walks, searching for a familiar glance, a familiar, loving gaze, a mischievous grin.

Sai had to be around here somewhere, both he and Gaster could sense her in their souls. She was nearby but hidden from their sight.  Hidden from their arms, embraces and kisses…

There was the sound of shattering plastic that jolted Grillby from his thoughts.  Gaster sighed, rubbing at his eye sockets, the remains of his phone shattered across the room.  Grillby decided to say nothing but look at him, eyebrow cocked.  He knew Gaster very well by now.  Grillby knew when Gaster needed words or physical contact, or when he needed the silence.  This was one of those times he needed the quiet.  To let his mind unload and reset.

Giving a shattering sigh, Gaster looked at Grillby.  His eye lights were dim, the bags under his sockets rivialing Sans’.  “I know you just came home, but let’s go out for a drink,” Gaster told him.  “I’m… I need a break.  I need to be out there. I’ve been here all day…”

“Hush. I get it.  Come on, there is a bar on the other side of the street I’ve been meaning to buy with your money. I think they call it the Long Island?”

With a snort, Gaster grabbed his coat and followed his lover out the door.  “Shut up or I might just.”

The door closed and locked behind them, the voices fading from the room.  The laptop hummed and continued to search, unknowing of its master’s departure.  Picture after picture, profile after profile it continued to search and discard.

Minutes later it gave a cheerful ping, On the screen was a picture of two seemingly identical, down to the freckles on their cheeks and noses, beautiful girls sitting in a darkened bar. Both with purple and red hair, bright hazel eyes sparkling at the camera.   “Great night @TheLongIslandBar with my favourite girls!” Sai had captioned.

* * * * *

Gaster and Grillby sat in a small booth, both nursing a glass of brandy.  “Has Stretch had any luck with his search?”  Grillby asked him.

“Last time I checked in with him he had none.  Though I suppose that was several hours ago so who knows what has happened with him.” Gaster shrugged, swirling the contents of his glass.  “I would ask him but it would probably help if I hadn’t destroyed my phone, and you didn’t forget yours at home.”

“And distract from the sight of my handsome mate in front of me?” Grillby winked.

You could practically see the gears grinding in Gaster’s mind.  His eye lights widened and there was a rising purple dusting to his cheekbones.  For all his intelligence, his scientific mind, throw in a flirty remark and you would be treated to the wonderful sight of a blushing Gaster.  He was still trying to gather his jaw off the floor when there was a familiar beside him.  “Excuse me sirs, but I must say.  I think this booth has both the hottest monster in the room and the best, cool drink of water in the whole club.  I always did like my water tall, dark and handsome.”  Grillby and Gaster turned sharply.  Long, shimmering purple hair, the ends red and those gorgeous hazel eyes twinkled at them.  How… after all their searching… how did they end up here in the same place?

Sai continued to speak, seemingly unnerved by their astonishment.  “Got room for one more?” she purred, settling in their other chair beside Gaster, leaning over the table, a smug smile on her lips.  She was utterly gorgeous as always and that tenor of voice made them weak every time.

Gaster took a swallow of scotch, trying to regain his voice but his cheeks remained purple.  He was so off his game today.  “There’s always room for you, sweetness.” He extended a hand to her.  “My name is W.D Gaster, and this is my long-time boyfriend, Grillby.”

“Gaster and Grillby, huh?” Sai pouted but shook their hands.  “It is a pleasure to meet the two of you.”

“The pleasure is ours,” Gaster said, taking her hand back and giving it a light kiss to the top of her hand.  “But please…. call me Doctor Gaster.” Grillby snorted quietly to himself.  The doctor line.

“Doctor… oh wow…” that mischievous sparkle returned to her eyes.  She must be planning something.  “So, tell me doc.  I have the sudden onset of palpitations and fever whenever I look at you or your handsome boyfriend.  Whatever could that be?”

Before any of them could respond, there was another voice beside them.

An identical female voice.

“Sai, this is where you ran off to!  Hiding your treasures from me. And here I thought you loved me, sister.”

A woman sat beside Grillby, tossing her purple and red hair back over her shoulder.  One eye seemed to be green instead of hazel, but other than that, they were perfectly identical.  “Will you at least introduce me to your new friends?” The woman asked, smirking at the two monsters.

Sai sighed and shook her head.  “Gaster, Grillby, meet my sister.  Her name is Ias.”

Ias grinned and extended her hand to the monsters.  “It is lovely to meet you all.”

Never, never in the history of resets or timelines had they ever seen a twin Sai.  Never.  There had been twin Papyruses, twin Gasters and Grillby’s.  There had been the time where they were professors and the girls their students and forbidden love interests. One of their personal favourites was when they all lived together in the mansion on the island. Hell, there had even been the gender-bent versions of them. 

There had never been twin Sai’s, no matter how much they had joked about it.

“Your eyes do not betray you.  You really are seeing double~” Ias purred with a wink.

Grillby chuckled, his mind swirling.  “Well, it works out.  Good looking girls are in such short supply. It’s a treat to see a natural beauty, but then when you see two, you know that you hit the jackpot.”

“Such a smooth mouth on you,” Ias commented, running her hand down his arm and resting her head against his shoulder.  “I would ask what you think, Sai, but it seems like you have already decided~”

Sai smirked, linking her arm through Gaster’s. “Oh, I have.” She purred before leaning in close to Gaster’s ear.  “My sister and I don’t like to share our toys very often,” she whispered, “but I know what she’s thinking.  And I think that we are going to make an exception for the two of you.”

Gaster chuckled, pulling her closer.  “If that’s the case, shall we hit your place?  Or ours?”


End file.
